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2005 H5N1 Sequences in Thailand Similar to 2004
September 1, 2005
Two HA sequences from 2005 H5N1 isolates (A/chicken/Thailand/Kamphaengphet-3-01/2005 and A/chicken/Thailand/Kamphaengphet-3-02/2005) from Thailand have become publicly available at the GenBank database in Japan. These are the first 2005 sequences from Thailand to become available. The two sequences are closely related to each other, and most closely related to more recent 2004 sequences from Thailand.
The close homology between the 2004 and 2005 HA sequences suggests that these isolates evolved from isolates in Thailand. There are some new polymorphisms, but most come from 2004 H5N1 isolates from Guandong province via recombination.
These results are not unexpected. H5N1 has become endemic in Thailand and H5N1 in domestic poultry has been reported to OIE multiple times in 2004 and 2005. The close relationship between the 2004 and 2005 isolates casts serious doubts on the lack of human cases in Thailand in 2005.
In Vietnam there were human cases in northern and southern regions in 2005. The 2005 isolates in the south are similar to 2005 isolates from Cambodia as well as 2004 isolates from Thailand, Laos, and Malaysia. The close relationship between these isolates in southeast Asia suggests the indigenous virus also causes human disease.
Thailand had a few cases reported in the media that had bird flu symptoms as well as exposures to dead birds from provinces experiencing H5N1 outbreaks. One case was also reported to be influenza A positive. The likelihood that patients with bird flu symptoms from H5N1 positives regions in Thailand is very high.
The lack of reported cases is cause for concern. The WHO intervention plan is to identify H5N1 cases early. The lack of any reported human cases from Thailand, Laos, and Malaysia in 2005 raises serious doubts about the viability of the intervention program.
These countries are unwilling or unable to identify H5N1 positive human cases. The monitoring of H5N1 in southeast Asia remains scandalously poor. As H5N1 wild bird flu migrates into the area, the monitoring deficiencies will increasingly put the world's health at risk.